Based on my experience, 90% of the time issues like that are related to the PC's sound driver. Rarely lang ang problem na ganyan na caused by the speaker hardware itself, those things are manufactured to last for a long period.

What they said, it is most probably just your driver, re-install. I had the same problem before tapos panic attack! but just went through the checklist, device connected - device identified by windows - installed driver - device manger check! - plugged in the speakers (green port) - plugged in the speaker power - all volumes maxed! - play gun's n roses welcome to the jungle for optimum speaker test!!